1. Field of the Invention
The invention relates to a semiconductor device. In particular, the invention relates to a shift register constituted using a transistor. Further, the invention relates to a display device provided with the semiconductor device, and to an electronic device provided with the display device.
It is to be noted that the semiconductor device here refers to a general device which can function by utilizing semiconductor characteristics.
2. Description of the Related Art
In recent years, a display device such as a liquid crystal display device and a light emitting device is actively developed in accordance with the increase of large display devices such as a liquid crystal display. In particular, a technique to integrate a driver circuit (hereinafter referred to as an internal circuit) including a pixel circuit, a shift register circuit, and the like over an insulator by using transistors formed of an amorphous semiconductor is actively developed, which largely contributes to the reduction in power consumption and cost. The internal circuit formed over the insulator is connected to a controller IC or the like (hereinafter referred to as an external circuit) through an FPC or the like and controlled in its operation.
For example, a shift register circuit which is constituted using only n-channel transistors formed of an amorphous semiconductor is suggested (for example, see Patent Document 1). However, the circuit disclosed in Patent Document 1 has a problem in that a noise is generated in a non-selection period since an output of the shift register circuit becomes a floating state in the non-selection period.
In order to solve this problem, a shift register circuit in which an output thereof does not become a floating state in a non-selection period is suggested (for example, see Non-Patent Document 1).
[Patent Document 1]
Japanese Translation of PCT International Application No. Hei 10-50024
[Non-Patent Document 1]
2.0 inch a-Si:H TFT-LCD with Low Noise Integrated Gate Driver SID'05 Digest p. 942-945